Front fork shudder / brake grab

On Apr 11, 1:46*pm, Anthony DeLorenzo
wrote:
On Apr 10, 9:19 pm, wrote:

I guess I am a bit surprised to hear that your CC fork suffers from
this. *I was actually considering replacing the SJ fork with an LHT
fork at some point precisely because my LHT seems so sturdy. *The CC
and LHT fork specs don't look that much different.

A few factors probably contribute. I am 6'6" 250 lb., riding a 62 cm
frame with a long head tube and steerer, and the linear-pull (V-brake)
is a lot of brake power for a road fork.

I'm more convinced that the problem is the rim. Even when I just
lightly apply the brakes and turn the wheel on the bike stand, it
noticeably grabs in the same spot every time. LBS has one of those
Mavic rim erasers, I'm going to borrow it and see if it helps.


http://ashwinearl.blogspot.com/2005/...juvinate..html

Steel wool soap pads also work great. Got 99c?

On Apr 11, 12:56*pm, Anthony DeLorenzo
wrote:
stopping the cable in a different spot, as suggested by a couple
of people (much appreciated!): It's a linear-pull brake, so the
housing runs straight from the handlebar to the brake noodle. No stops
involved. Unless I'm not understanding what you propose.

Sorry, comprehension error on my part (at least); I read right past
the words "linear-pull" and "287V". As far as I know, V-brakes are
immune to the bending head tube issue, because they always have a full
run of housing from the lever to the brake.

On Apr 11, 11:57 am, landotter wrote:
http://ashwinearl.blogspot.com/2005/...tip-how-to-rej...

Steel wool soap pads also work great. Got 99c?

Great link. I'm going to see if the local Canadian Tire carries a
product like that.

Thanks,
Anthony

Anthony DeLorenzo wrote:
Thanks to all for the responses so far. I double-checked everything to
do with the calipers, pads, and wheel trueness. I was able to reduce
the problem but not eliminate it.

I did notice that the brakes are consistently grabbing at one specific
section of the rim. I can't see any difference in the rim itself that
would cause this. I didn't have this problem when the wheel was
mounted on my mountain bike, but the stiffer fork may have just
absorbed it better.

I'm going to try a wheel swap tonight and see if it eliminates the
problem.

Please do keep the thread updated. This has been a chronic problem on
my Raleigh One-Way despite the best efforts of shops, some friends, and
myself. I think they that my bike just came with a crappy fork that
flexes too much. I'll try new front wheels tomorrow too.

\\paul
--
Paul M. Hobson
..:change the f to ph to reply:.

On Apr 11, 7:04*pm, "Paul M. Hobson" wrote:
Anthony DeLorenzo wrote:
Thanks to all for the responses so far. I double-checked everything to
do with the calipers, pads, and wheel trueness. I was able to reduce
the problem but not eliminate it.

I did notice that the brakes are consistently grabbing at one specific
section of the rim. I can't see any difference in the rim itself that
would cause this. I didn't have this problem when the wheel was
mounted on my mountain bike, but the stiffer fork may have just
absorbed it better.

I'm going to try a wheel swap tonight and see if it eliminates the
problem.

Please do keep the thread updated. *This has been a chronic problem on
my Raleigh One-Way despite the best efforts of shops, some friends, and
myself. *I think they that my bike just came with a crappy fork that
flexes too much. I'll try new front wheels tomorrow too.

http://www.bikemannetwork.com/biking...RKLEVRD/BR7212
+
Cheap Tektro LP arms and you get kick butt and easy to set up braking.
Not as classic looking as cantis--but sooo not fussy. $55 or so and
you're stopping like a champ.

I'd try a new wheel first. ;-)

Anthony DeLorenzo wrote:
On Apr 10, 9:19 pm, wrote:

I guess I am a bit surprised to hear that your CC fork suffers from
this. I was actually considering replacing the SJ fork with an LHT
fork at some point precisely because my LHT seems so sturdy. The CC
and LHT fork specs don't look that much different.

A few factors probably contribute. I am 6'6" 250 lb., riding a 62 cm
frame with a long head tube and steerer, and the linear-pull (V-brake)
is a lot of brake power for a road fork.

I'm more convinced that the problem is the rim. Even when I just
lightly apply the brakes and turn the wheel on the bike stand, it
noticeably grabs in the same spot every time. LBS has one of those
Mavic rim erasers, I'm going to borrow it and see if it helps.

It could just be some initial wear-in issues as well. With tinkering
and riding the problem has improved, at least to the point where the
front brake is now quite usable, although still annoying.


I'd guess it's the wheel also. I'm 6'10"/230. I have several bikes with
several types of brake setup. The only time I had a problem with shudder
was with a Mavic front rim that came without the anodizing removed on
the brake track. It took a long time (months) to wear through, and until
it did, it was scary grabby.

Anthony DeLorenzo Wrote:
Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim
- check pad angle
- check for play in calipers
- check headset (already ruled out)
- new pads
- different wheel


I'll try these things when I go home tonight, but from what I've read
these problems can be hard to fix. Any other advice or suggestions
would be appreciated.

Regards,
Anthony
I wonder if the rim has good lateral runout.
If you remove the tire and run a set a calipers around on the braking
surface to see if the outside rim width is consistent, you will know.
You would also know by watching the action of the brake arms as they
hold down on the rim.


--
daveornee

On Apr 12, 7:53*am, daveornee daveornee.37r...@no-
mx.forums.cyclingforums.com wrote:
Anthony DeLorenzo Wrote:

Hi All,

I took my road bike out for its maiden voyage last night. The front
brakes were grabbing and causing the front fork to shudder terribly.
Basically unusable. The set-up is a Surly crosscheck frame and fork,
Avid SD-5 brake (linear pull), Dia Compe 287V lever, Kool Stop salmon
pads (used), Velocity Dyad rim.

I did a newsgroup search and came up with some things to check out:

- ensure rim is true, especially the vertical trueness
- clean rim
- check pad angle
- check for play in calipers
- check headset (already ruled out)
- new pads
- different wheel

I'll try these things when I go home tonight, but from what I've read
these problems can be hard to fix. Any other advice or suggestions
would be appreciated.

Regards,
Anthony

I wonder if the rim has good lateral runout.
If you remove the tire and run a set a calipers around on the braking
surface to see if the outside rim width is consistent, you will know.
You would also know by watching the action of the brake arms as they
hold down on the rim.

Very true! I just build two wheels to replace a couple of rims with
short flat spots from an impact with a concrete lip. You could
visually inspect the rims by casually spinning them--and they seemed
quite reasonable--I felt a little silly replacing them--but the
braking was atrociously grabby at that flat spot. Nothing short of re-
rimming resolved the problem.

Well, the problem has been solved.

I took off the Kool Stop pads and went with a cheap set of Avid pads
that aren't as grabby, set up with a generous toe-in. I also swapped
out the wheel (Velocity Dyad rim) for another rim that is a Sun CR18.

At some point I will try the old wheel with the new pads, just to see
if it helps, but for now the bike is happy and I am happy.

Thanks to everyone for all the advice on this thread, especially re
toe-in. I have never had to toe-in a V-brake before, they normally
perform just fine without it, IME.

Regards,
Anthony

On Apr 12, 5:53 am, daveornee daveornee.37r...@no-
mx.forums.cyclingforums.com wrote:

I wonder if the rim has good lateral runout.
If you remove the tire and run a set a calipers around on the braking
surface to see if the outside rim width is consistent, you will know.
You would also know by watching the action of the brake arms as they
hold down on the rim.

Now that I have that wheel off the bike I am going to examine it more
closely. I did a basic check with calipers on the rim width in a
couple of spots, but spinning the wheel should give a better
indication. I wouldn't be surprised if the rim is off.